SCOTTSDALE, Ariz. (April 17, 2011) -- Armed with a five-shot lead going into Sunday’s final round of the Arizona Stroke Play Championship, Peter Kyo Won Koo knew that he could make history as the state’s youngest amateur winner ever.

Good thing the 15-year-old from Chandler also had the foresight to guard against the headiness of such a golden opportunity, because after just five holes at the TPC Champions Course, his big lead was gone with the wind.

“Before I started my round, I told myself, ‘Don’t think about that, being the youngest winner or whatever,’ ’’ said Koo, who is a freshman on the Hamilton High golf team. “And don’t think about the five-shot lead, either.

“Just imagine you’re playing a one-day tournament, and that everything is starting at even (par).’’

Obviously, Koo is wise beyond his years. How else do you explain blowing the five shots and then battling back in blustery conditions compounded by tough pin placements to win by two strokes over Alex McMahon, a teen-ager from Tucson? “It’s weird, but it’s also amazing,’’ observed Koo, who erased a standard held by the late Bob Goldwater (1926 Arizona Amateur) and Philip Francis (2005 Arizona Public Links), who were 16 when they won major championships sponsored by the Arizona Golf Association. Koo did it with a gutsy, 4-over-par 74 that left him with a winning total of even par 280. Despite the four straight bogeys beginning at the second hole and a double bogey at the par-3 13th, Koo’s three birdies were good enough to best McMahon, 18, a University of Arizona-bound recruit whose 69 was the day’s best score.

Big hitter Camron Howell of Queen Creek finished third, four strokes back after a 73. David Lowe, an 18-year-old from Scottsdale who is headed to Arizona State, was fourth with a 71 that left him at five off the pace.

In a tie for sixth were Scottsdale’s Justin Hardin and Andrew Medley, who both carded 75s to finish six shots back. At one point, Medley, a former Arizona standout and touring pro, had a share of the final-round lead with Koo after birdies at the fourth and fifth holes.

Koo’s win marked the fifth year in a row that a player from Hamilton High has won this tournament, as Koo followed alums Andrew Yun (2007, 2009) and Chan Kim (2008, 2010). Asked about keeping the streak alive, the cool-headed Koo just laughed.

“I never even knew when I came to Hamilton that they had won (the state high school championship) five years in a row,’’ he said. “So it’s all good, I guess.’’

That’s certainly how it all played out for Koo on Sunday, as Medley and then McMahon kept the pressure on. But Medley, the club champ at Whisper Rock, was felled by a disastrous triple-bogey at the seventh hole that began with a tee shot OB, and McMahon never got closer than one shot as his Achilles heel came early with three-putt bogeys at holes No. 2 and 5.

“It got a little windy out there, but I felt good coming into the final round,’’ said McMahon, whose best finish in AGA events had been a tie for seventh last month in the Arizona Publinks. “I guess I hit it poorly yesterday (74), but I definitely found something when I was warming up.’’

Birdies at Nos. 1, 9, 12 and 15 got McMahon to within one shot of Koo. But Koo also birdied the 15th and that was the final margin as both players finished off their rounds par, par and bogey.

Koo, who plays it pretty low key, had plenty of support, as his personal instructor, Sinclair Torrilhon, and Hamilton High coach, Steve Kanner, joined Koo in his march to the title that began when he grabbed a share of the second-round lead. Both predicted the Stroke Play was just the first of many major accomplishments for their pupil/player.

“He’s mature beyond his years,’’ noted Kanner of Koo, who has won over 40 junior tournaments, including the recent Thunderbird Invitational.

“He’s a hard worker, he’s smart, and from a coach’s perspective, he’s the total package.’’

Torrilhon echoed those thoughts: “He’s got such a good attitude; never gets too high or too low. That’s why he’s a great worker and a talent. And he’s such a good student when it comes to implementing changes. He gets it.’’

But Koo didn’t exactly get it when it came to the prize he was awarded as winner of the Stroke Play -- a Kachina doll. Told he would get the beautiful Native American replica of a warrior dancing in full garb, Koo, who was born in Seoul, South Korea and moved to the U.S. in 2007, said he had never heard of such a thing.

“It kind of looks like a bird,’’ he said with a laugh. “Then again, I’m learning a lot of new things today.’’

As the youngest winner ever of an AGA event, he’s got that right, said Ken Kellaney, perhaps the organization’s greatest player ever as evidenced by his 10 POY awards.

“When I was that age, I couldn’t tie my shoes,’’ said Kellaney, whose closing 71 got him into the tournament’s top 10 (ninth).

“So my hat’s off to him. That was some shootin’ that got him that win.’’